Lewis, who's headed to the Superbowl in New Orleans this weekend, looked into using a nasal spray made of deer antler velvet to heal his torn right triceps, Sports Illustrated reported in their February 4 issue. Lewis denies the story, calling the rumor a "trick of the devil," according to USA Today.

Made from male deer antlers during the stage when the antlers are covered in soft fuzz, the unproven performance enhancer is often used by athletes who believe it helps heal cartilage and tendon injuries more quickly and boosts strength and endurance.

Even so, it's a big business, especially in New Zealand, a major exporter of deer velvet, which ships tens of millions of dollars worth of the substance to Asia and the U.S. each year, according to the New York University Langone Medical Center.

Deer farming is a huge industry in the country, with about 2,800 farmers that own approximately 1.1 million deer, most of them red deer, elk, and red deer-elk hybrids, according to the company New Zealand Deer Velvet.

Before removing the velvet from a stag's antlers, certified veterinarians or farmers give the animal stag a local anesthetic to minimize stress.

We asked a few medical experts to give us the facts on deer antler velvet.

Growth hormones, which are naturally produced by the brain and liver, regulate how our bodies grow. If the body doesn't produce enough growth hormones, dwarfism can occur; too much, and a person may get acromelagy, a type of gigantism. (See a human-body interactive.)

Doctors give growth hormones to young people with stunted growth, but they don't recommend it for athletes or bodybuilders, according to Spyros Mezitis, an endocrinologist at Lenox Hill Hospital in New York City.

That's because many athletes take several times the recommended dosage, which can result in adverse effects, Mezitis said. For example, too much IGF-1 may cause tendons to become too tight and break or may disrupt how the body metabolizes fats and sugars.

What Does It Do?

Early research shows that IGF-1 may be effective in healing some cartilage and tendon injuries, noted Leon Popovitz, an orthopedic surgeon and founder of New York Bone & Joint in Manhattan.

A recent study found that taking IGF-1 supplements is linked to improving cartilage damage in joints due to repetitive trauma, Popovitz said.

Even so, such studies are still very preliminary, and growth hormone research is still unproven, he cautioned. At the moment, deer antler velvet is available as an unregulated supplement.

"What often happens is these supplement companies grab these promising [hormone] factors, jump on them, and market them before the entire medical community has the ability to know the real detrimental effects," Popovitz said.

How Does It Work?

IGF-1 affects how the body repairs itself. First, the hormone aids in building up a matrix or base—essentially a building block of protein—that's needed for cells to grow.

Then, the substance increases the number of new cells that accumulate on that base, which get busy healing the injury.

What's the Bottom Line?

IGF-1 has shown promise for helping kids with stunted growth or people with dwarfism, as well as for healing cartilage or tendon injuries. It should not be used without a doctor's care, especially as a performance enhancer.